Display panel substrates of liquid crystal display apparatuses or the like are usually produced using glass substrates, which are brittle material substrates. A liquid crystal display apparatus is produced by assembling a pair of glass substrates with an appropriate gap interposed therebetween and then enclosing a liquid crystal material in the gap.
For producing such a display panel substrate, an assembled mother substrate produced by assembling a pair of mother glass substrates is scribed and broken. Thus, a plurality of display panel substrates are produced from the assembled mother substrate. A substrate scribing and breaking method used for scribing and breaking an assembled mother substrate is disclosed in Japanese Laid-Open Publication No. H6-48755 (patent document 1).
FIGS. 15A through 15D show steps of scribing and breaking a mother substrate described above. In the following description, for the sake of simplicity, among a pair of mother glass substrates facing each other which are assembled together to produce an assembled mother glass substrate, one mother glass substrate will be referred to as the “A side glass substrate” and the other will be referred to as the “B side glass substrate”.
(1) First, as shown in FIG. 15A, an assembled mother substrate 901 is placed on a first scribing device with an A side glass substrate of the assembled mother substrate 901 as an upper substrate. Using a cutter wheel 902, a scribe line Sa is formed in the A side glass substrate.
(2) Next, the assembled mother substrate 901 with the scribe line Sa formed in the A side glass substrate is inverted, and the assembled mother substrate 901 is transported to a first breaking device. In the first breaking device, as shown in FIG. 15B, the assembled mother substrate 901 is placed on a mat 904. A break bar 903 is pressed on the B side glass substrate of the assembled mother substrate 901 along the scribe line Sa formed in the A side glass substrate. By this operation, a vertical crack extends upward from the scribe line Sa in the A side glass substrate which is placed as a lower substrate, and the A side glass substrate is broken along the scribe line Sa.
(3) Next, the assembled mother substrate 901 with the A side glass substrate being broken is transported to a second scribing device without inverting the assembled mother substrate 901. In the second scribing device, as shown in FIG. 15C, a surface of the B side glass substrate of the assembled mother substrate 901 is scribed using the cutter wheel 902, and thus a scribe line Sb is formed parallel to the scribe line Sa. The scribe line Sb formed in the B side glass substrate is often formed offset in the horizontal direction from the scribe line Sa formed in the A side glass substrate. The reason is that the assembled mother substrate 901 has a plurality of display panel areas and an electrode terminal portion needs to be formed on a peripheral portion of one of the glass substrates of the display panel substrate.
(4) Then, the assembled mother substrate 901 is inverted to put the A side glass substrate as the upper substrate, and is transported to a second breaking device. In the second breaking device, as shown in FIG. 15D, the assembled mother substrate 901 is placed on the mat 904. A break bar 903 is pressed on the A side glass substrate, at a portion corresponding to the scribe line Sb formed in the B side glass substrate, along the scribe line Sb. By this operation, the B side glass substrate as the lower substrate is broken along the scribe line Sb.
By performing the above steps (1) through (4), the assembled mother substrate 901 is scribed and broken at a desired position.
The above-described substrate scribing and breaking method requires an inversion step for inverting the assembled mother substrate in order to scribe and break one of the mother glass substrates of the assembled mother substrate, and a breaking step of breaking the one mother glass substrate by extending a vertical crack formed by scribing the one mother glass substrate. There is a problem that a substrate scribing and breaking device for performing these steps requires a complicated structure and a large area for installment.
The above-described substrate scribing and breaking method also has a problem that a demand for reducing the production cost of display panels cannot be fully met.
A method used in a conventional breaking step, i.e., a method of pressing a rear surface of a substrate along a scribe line to scribe and break the substrate, has a problem that an edge of a broken surface of the substrate is, for example, easily chiseled off.
The present invention, for solving these problems, has an objective of providing a method for scribing and breaking a substrate efficiently without requiring a complicated device.